Health Briefs

August 23, 2002

A New Weapon Against Anthrax?

In this week’s journal Nature, scientists have reportedly identified an enzyme that is capable of recognizing and destroying both the inactive spores and the active form of the anthrax bacillus.  The enzyme is naturally produced by a virus that specifically targets bacteria, including anthrax.  The enzyme, PlyG, is a member of the lysin family of enzymes, which cause a lethal disruption of susceptible bacteria.  What is especially interesting about this study is that PlyG appears to be effective in killing the dormant spores of anthrax as well as the active bacillus.  Like other bacilli, anthrax bacteria can transform themselves into a spherical “vegetative spore” when environmental or nutritional conditions are inadequate to sustain the bacterial cells’ needs.  These spores are extraordinarily resistant to extremes of temperature, dryness, and lack of nutrients, as well as to the presence of antibiotics or antiseptics.  PlyG appears to specifically and efficiently target both forms of the anthrax bacterium, and without apparent toxicity to the mice that were experimentally infected with the deadly bacterium.   PlyG was able to kill anthrax bacteria in both test tubes as well as in mice that were infected with anthrax.  When compared to infected mice receiving a placebo, anthrax-infected mice that received PlyG were significantly more likely to survive their anthrax infections.  This study offers hope for a new and potentially highly effective treatment for victims of anthrax infection, a disease that is 99% fatal when left untreated.

In this week’s Journal of the American Medical Association (JAMA), the impact of cataracts on the incidence of motor vehicle accidents among elderly drivers was assessed.  The term cataract describes the changes that occur in the lenses of the eyes of many elderly people.  When the lens loses its transparency and become hazy, a person is said to have cataracts.  Cataracts can significantly impair vision, and the cloudy lens is often removed and replaced with a plastic lens that is surgically inserted into the eye.  Excessive and chronic exposure of the eyes to the sun and other sources of ultraviolet radiation, and some medicines (steroids and some cancer treatment drugs, for example), can increase the risk of cataract formation.

In the JAMA study, 277 volunteers with cataracts, aged 55 to 84 years, were followed for a period of 4 to 6 years.  The incidence of motor vehicle accidents was then compared among those volunteers choosing to have cataract surgery (174 people) and those who chose not to undergo surgery (103 people).  The study found that half as many volunteers who had undergone cataract surgery had accidents when compared to the non-surgery group.  It is not clear how well balanced both groups were in terms of other serious health problems that might also have impacted on the motor vehicle accident rate.  It is possible, for example, that the patients who chose not to undergo cataract surgery might have had other serious ailments that made them poor surgical risks, and that these additional medical problems, if any, might have played a role in the increased number of accidents in this group.  Still, this is an intriguing study, and at least suggests that the presence of significant cataracts may increase the risk of motor vehicle accidents when left untreated.

Gingko biloba is among the most widely used non-prescription herbal supplement in the world.  Many claims have been made for the effects of gingko, including the ability to enhance blood flow to the brain and, in the process, to improve memory and overall brain function.  Gingko has also been proposed as a treatment for Alzheimer’s disease, ringing in the ears (tinnitus), altitude sickness, and arterial disease of the legs.  Gingko is known to have a high concentration of antioxidants, called biflavones, and is therefore thought to have potential anti-inflammatory and anti-cancer effects, although there is not much scientific data to support such claims.  When taken in large quantities, gingko can also thin the blood, causing an increased risk of bleeding in response to surgery or trauma.

In the JAMA study, the effects of gingko on memory were studied in people older than 60 years (98 men and 132 women).  Study volunteers were randomly assigned to take 120 mg of gingko biloba per day (115 volunteers) or placebo pills (115 volunteers).  All study volunteers were then studied over a 6 week period with standard tests that measure memory capability.  Baseline memory tests, performed at the beginning of the study, revealed no significant differences in memory function between the two groups of volunteers.  At the end of 6 weeks, the study found no significant improvements in the group taking gingko with respect to learning, memory, attention, or concentration.  These findings are consistent with most of the recent literature regarding gingko’s effects on memory.

Air Pollution & Heart Function During Exercise

In the current journal Circulation, a study of 45 Finnish adults with stable coronary artery disease was performed to look at the effects of air pollution on heart function during exercise EKG studies.  The 45 heart patients underwent a total of 342 exercise EKGs over a period of 6 months.  During each exercise episode, particulate air pollution levels were measured and recorded.  The study found that elevated concentrations of fine particulate pollutants in the air were associated with a greater than threefold risk of EKG signs of heart ischemia (inadequate oxygen delivery to the heart muscle).  This study, therefore, suggests that, at least in patients with preexisting heart disease, the presence of high levels of fine particulate air pollution may significantly increase the risk of cardiac ischemia during periods of exercise.  The metabolic demands of exercise may stress an already diseased heart, and the superimposed effects of air pollution, it would appear, may aggravate problems with cardiac function even further.

The current issue of the Journal of the National Cancer Institute (JNCI) contains an analysis of past studies that looked at the breast cancer susceptibility genes BRCA1 and BRCA2.  To date, these are the only two gene mutations that have been linked with an increased risk of developing breast cancer.  When first discovered, it was thought that more than 80% of women with either of these mutations would eventually develop breast cancer by 70 years of age.  Subsequently, the increase in risk has been revised downward to 35-50% in a number by a number of studies.  (These same gene mutations have also been linked with an increased risk of ovarian and prostate cancer as well.) 

The JNCI study’s analysis suggests that previous estimations of breast cancer risk due to these two gene mutations have probably been overestimated.  The author of this study criticized previous BRCA1 and BRCA2 studies for not completely accounting for additional breast cancer risk factors, such that the estimated increase in the risk of developing breast cancer due solely to BRCA1 or BRCA2 is likely to have been overestimated.  Because such prior studies preferentially looked at women from families with a high incidence of breast cancer, other potential risk factors were likely present but not appreciated.  The recommendation is that future studies on the breast cancer impact of these two gene mutations take greater care in accounting for other coexisting breast cancer risk factors among study volunteers.

Dr. Robert A. Wascher